1. Field of the Invention
The invention relates to driving devices for use with tubular members and more particularly to an improved strap wrench.
2. Description of the Prior Art
Strap wrenches have been in existence for over 100 years to drive tubular members. Strap wrenches use a flexible strap positioned and tightened around the tubular member to transmit a turning force to the tubular member. These devices usually consist of a strap loop anchored at one end to a handle. Its other end is connected to a clamping means on or in the handle to draw the strap tightly around the tubular member to allow the application of torque through the strap to the tubular member.
Strap wrenches may be used for many different applications. Since engine oil filters are of such a large diameter that they can not be turned with most traditional wrenches, a strap wrench is the ideal tool for removing and replacing the filter. Equally, water and gas pipes are usually located in areas where there is very little room to work. A properly designed strap wrench is capable of turning pipes in restricted areas where traditional wrenches, such as monkey wrenches, are not capable of functioning. Similarly, strap wrenches may be used to open and close jars or bottles.
While the concept of the use of a strap for such purposes has been known for a number of years, the method of construction of strap wrenches has markedly varied over time with developments in materials and construction techniques as can be seen in the following: U.S. Pat. No. 1,525,358 issued to Bergen on Feb. 3, 1925; U.S. Pat. No. 1,916,554 issued to Bevington et al. on Jul. 4, 1933; U.S. Pat. No. 2,004,830 issued to Rector on Jun. 11, 1935; U.S. Pat. No. 2,081,383 issued to Rector on May 25, 1937; U.S. Pat. No. 2,128,991 issued to Eighmey on Sep. 6, 1938; U.S. Pat. No. 2,232,882 issued to Martino on Feb. 25, 1941; U.S. Pat. No. 2,481,055 issued to Whitaker on Sep. 6, 1949; U.S. Pat. No. 2,557,601 issued to Hebden on Jun. 19, 1951; U.S. Pat No. 2,960,896 issued to Long on Nov. 22, 1960; U.S. Pat. No. 4,145,938 issued to Laird, Jr. on Mar. 27, 1979; and U.S. Pat. No. 4,345,494 issued to Aamodt on Aug. 24, 1982.
U.S. Pat. No. 4,532,833 issued to Downs on Aug. 6, 1985 discloses a strap wrench which has both ends of the strap anchored in a slot in the center of the handle. The device contains an adjustable slide member which controls the size of the loop formed by the strap. Such a device limits the use of the device when the end of the tubular member is not accessible.
U.S. Pat. No. 6,125,723 issued to Huang on Oct. 3, 2000 discloses a strap wrench where one end of the strap is fixed to the handle. The other end of the strap is pulled through a channel on the handle and is locked into place by a pivotally mounted toothed cam which is positioned by the user against the strap. This, in conjunction with a pawl on the handle, holds the strap tightly in place and transmits force from the handle through the strap to the tubular member. The engagement of the cam with the strap requires the user to actively engage in pressuring the cam in position and the cam teeth into the strap.
It is an object of the present invention to allow tightening of the strap of a strap wrench in accordance with the present invention around the tubular member without applying pressure to the rocker arm.
It is also an object of the present invention to create a strap wrench where the strap is automatically locked in position.
It is also a further object of the present invention to create a strap wrench with allows the user to release the strap by simply applying pressure to a rocker arm on the handle of the wrench
It is a further object of the invention which allows the user to change the strap when necessary due to wear on the strap or for use with different sized pipes, oil filters, jars and the like.
It is an additional object of the present invention to creating a strap wrench which reduces the wear on the strap.
The present invention is a strap wrench comprising a handle and detachable strap. The handle has an enlarged opening for receiving and holding one end of the strap. One end of the strap is enlarged and shaped to be received in said enlarged opening in the handle. While removable, when the enlarged end of the strap is so placed in the enlarged opening in the handle, the strap is anchored at that end
The handle has a lengthwise channel passing through it through which the other end of the strap passes. The strap is held in place in the channel by means of a rocker arm which is biased by a spring to press the strap against the far wall of the channel when the strap is positioned in the channel. The surface of the rocker arm which engages the strap has a means for frictionally engaging the strap such as grooves, teeth, roughened surface or a layer of high friction material such as a rubber pad. In addition or as a alterative, the surface of the channel opposite the point of contact of the rocker arm may have a similar friction means for engaging the strap when the strap is pressed against it.
When the strap is drawn through the channel, the strap creates a loop above the top of the handle for placement around the tubular member which requires turning. The strap is initially positioned in the channel by the user pressing one side of the rocker arm to release and open the channel. Once the strap is initially seated, the rocker arm may be released and the loop may be tightened by pulling the strap through the channel since this will act to move the contact between the strap and the rocker arm to a portion of the rocker arm without a friction means. Once the rocker arm is released, the loop may only be enlarged by applying pressure to one side of the rocker arm. Free movement of the strap may also be enhanced by applying pressure to the rocker arm. The strap of the strap wrench may have rows of projections on its surface to aid in gripping the tubular object to which torque is to be applied.
Due to the flexibility of the strap, the strap wrench may also be used on non-circular tubular objects. Further uses and advantages will become apparent from the detailed description of the preferred embodiment.